Substituted pyrazolylpyrazole derivative and use of same as herbicide

ABSTRACT

Provided is a compound capable of effectively control worst weeds of higher leaf stages that present practical problems. A specific pyrazolylpyrazole derivative of formula (I) is disclosed that is able to solve the above-mentioned problems.

TECHNICAL FIELD

The present invention relates to a substituted pyrazolylpyrazole derivative and the use of that compound as a herbicide.

BACKGROUND ART

Numerous herbicides have recently come to be used in the cultivation of agricultural crops, and have contributed to reduced labor for farmers and improved productivity of agricultural crops. Numerous herbicides are also used practically in the cultivation of field and paddy rice.

However, there is considerable diversity in the species of weeds, the germination and growth periods of each species of weed are not uniform, and the growth of perennial weeds extends over a long period of time. Consequently, it is extremely difficult to control all weeds with a single spraying of herbicide.

Early to mid-term one-shot herbicides have been shown to be effective for paddy rice by treating during the second to third leaf stage of paddy weeds (generic term for Echinochloa oryzicola, Echinochloa crus-galli var. crus-galli, Echinochloa crus-galli var. formosensis, Echinochloa crus-galli var. praticola and Echinochloa crus-galli var. caudata), and major weeds can be controlled by a single treatment (see Non-Patent Document 1). However, it is extremely difficult to control paddy weeds that have grown to the 3.5 leaf stage or more with early to mid-term one-shot herbicides currently in practical use, and the control of paddy weeds in the third leaf stage and control of paddy weeds in the 3.5 leaf stage are technically completely different.

Moreover, maintaining herbicidal effects (or residual activities) over a long period of time is important in terms of reducing spraying of agricultural chemicals, saving on labor and curtailing costs, and is considered to be an essential area of performance for early to mid-term one-shot herbicides.

In addition, acetolactate synthase (ALS) inhibitors have come to be widely used in recent years, and weeds exhibiting resistance to ALS inhibitors have become a problem. There are few herbicides demonstrating adequate efficacy against ALS inhibitor-resistant biotypes of the perennials of Sagittaria trifolia and Sagittaria pygmeae. In addition, examples of perennial weeds that have caused problems in recent years include Eleocharis kuroguwai, Scirpus planiculmis and Scirpus nipponicus, while examples of annuals include Aeschynomene indica, Leptochloa chinensis and Murdannia keisak and there are few herbicides that demonstrate adequate efficacy against these difficult-to-control weeds.

On the other hand, numerous pyrazole derivatives are used practically as herbicides, and although pyrazole derivatives such as

-   4-(2,4-dichlorobenzoyl)-1,3-dimethyl-5-pyrazolyl p-toluenesulfonate     (common name: “Pyrazolate”), -   2-[4-(2,4-dichlorobenzoyl)-1,3-dimethylpyrazol-5-yloxy]acetophenone     (common name: “Pyrazoxyfen”) or -   2-[4-(2,4-dichloro-m-toluoyl)-1,3-dimethylpyrazol-5-yloxy]-4′-methylace     tophenone (common name: Benzofenap”) are widely used, their     registered application range for paddy weeds in Japan when used     alone is up to the 1.5 leaf stage, and although these pyrazole     derivatives are effective against a wide range of weeds, the     efficacy thereof is not always adequate against paddy weeds of     higher leaf stages.

In addition, although Compound 73 of Example 4 described in WO 94/08999 in the form of

-   1-(3-chloro-4,5,6,7-tetrahydropyrazolo[1,5-a]pyridin-2-yl)-5-[methyl(pro     p-2-ynyl)amino]pyrazole-4-carbonitrile (common name: “Pyraclonil”)     is effective against a wide range of weeds, its efficacy against     paddy weeds of higher leaf stages is inadequate, and the registered     application range in Japan against paddy weeds when using this     herbicide alone is up to the 1.5 leaf stage.

Moreover, although WO 94/08999 also discloses compounds that demonstrate herbicidal effects by treating weeds that grow on farmland before and after growth, since there is no description regarding leaf stage, it cannot be said that these compounds have adequate effects against weeds of higher leaf stages. In addition, although isopropyl ammonium N-(phosphonomethyl) glycinate (common name: “Glyphosate Isopropylamine Salt”), for example, is widely used as a herbicide that demonstrates a wide range of effects against farmland weeds, problems have arisen in recent years regarding its efficacy against resistant weeds.

In addition, there has recently been growing concern over pollution of groundwater and rivers by pesticides. Consequently, there is a need for the development of herbicides that minimize effects on the environment such as by lowering the risk of runoff of active ingredients to locations other than locations of their intended application.

CITATION LIST Patent Literature Document

-   Patent Document 1: WO 94/08999

Non-Patent Literature Document

Non-Patent Document 1: “Suiden Zasso no Seitai to Sono Bojo—Suitosaku no Zasso to Josozai Kaisetsu (Ecology of Paddy Weeds and their Control—Explanation of Weeds of Rice Paddy Crops and Herbicide)”, p. 159

SUMMARY OF THE INVENTION Technical Problem

An object of the present invention is to provide a compound that has superior characteristics as an herbicide ingredient, such as having a wide herbicidal spectrum including weeds that are resistant to existing herbicides, being able to control worst weeds of higher leaf stages that present practical problems, and not causing phytotoxicity to crops such as paddy rice.

Solution to Problem

As a result of conducting extensive studies to achieve the aforementioned object, the inventors of the present invention found that a pyrazolylpyrazole derivative having a specific chemical structure especially exhibits a wide herbicidal spectrum over a long period of time, demonstrates superior herbicidal efficacy against worst weeds of higher leaf stages, and has adequate safety with respect to cultivated crops, thereby leading to completion of the present invention on the basis of these findings. Thus, the present invention provides a pyrazolylpyrazole derivative in the form of a compound represented by the following formula (I):

In the above formula,

R¹ represents a chlorine atom or bromine atom,

R² represents a cyano group or nitro group,

R³ and R⁴ may be the same or different and represent C₁-C₆ alkyl groups (which may be substituted with one or more halogen atoms depending on the case), C₃-C₆ alkenyl groups (which may be substituted with one or more halogen atoms depending on the case), or C₃-C₆ alkynyl groups (which may be substituted with one or more halogen atoms depending on the case),

a represents 3 to 5, and

X represents an oxygen atom or sulfur atom.

Preferably,

in formula (I),

R³ and R⁴ may be the same or different and represent C₁-C₄ alkyl groups (which may be substituted with one or more halogen atoms depending on the case), or C₃-C₅ alkenyl group (which may be substituted with one or more halogen atoms depending on the case), and

a represents 4

In the present description:

the mark “C_(a)-C_(b)” which is followed by a substituent means that the substituent has a to b carbon atoms.

Fluorine, chlorine, bromine and iodine atoms are included in “halogen atoms”.

“Alkyl” as referring to a group per se or a moiety of a group can be linear or branched, and although there are no limitations thereon, examples thereof include methyl, ethyl, n- or isopropyl, n-, iso-, sec- or tert-butyl, n-pentyl and n-hexyl groups, and each is selected within a range of the specified number of carbon atoms thereof.

An “alkenyl group” refers to an unsaturated hydrocarbon group that is linear or branched and has one or two or more double bonds in a molecule thereof, and although there are no limitations thereon, specific examples thereof include a vinyl group, 1-propenyl group, 2-propenyl group, 2-butenyl group, 2-methyl-2-propenyl group, 3-methyl-2-butenyl group and 1,1-dimethyl-2-propenyl group, and each is selected within a range of the specified number of carbon atoms thereof.

An “alkynyl group” refers to an unsaturated hydrocarbon group that is linear or branched and has one or two or more triple bonds in a molecule thereof, and although there are no limitations thereon, specific examples thereof include an ethynyl group, 1-propynyl group, 2-propynyl group, 1-butynyl group, 2-butynyl group, 3-butynyl group and 1,1-dimethyl-2-propynyl group, and each is selected within a range of the specified number of carbon atoms thereof.

In the case of the “alkyl group”, “alkenyl group”, and “alkynyl group”, at least one hydrogen atom contained in these groups may be substituted with a halogen atom, and although there are no limitations thereon, examples thereof when using the example of an alkyl group include chloromethyl, dichloromethyl, trifluoromethyl, chloroethyl, dichloroethyl, trifluoroethyl, tetrafluoropropyl, bromoethyl, bromopropyl, chlorobutyl, chlorohexyl and perfluorohexyl groups, and each of these is selected within a range of the specified number of carbon atoms thereof.

In the case where the aforementioned group or moiety is substituted with a plurality of halogen atoms, that group can be substituted with more than one halogen atoms that are the same or different.

In addition, in the case of having stereoisomers, the cis form and the trans form are included. The present invention also relates to all stereoisomers and mixtures thereof which are included in the compound represented by formula (I) but are not specifically defined.

In all of the formulas listed below, substituents and symbols have the same meanings as defined for formula (1) unless specifically defined otherwise. The compounds of formula (I) provided by the present invention in which R³ is a hydrogen atom can easily be synthesized by a carbamation reaction from a compound represented by formula (II).

The compound of formula (II) can be synthesized from tetrahydro-2H-pyran-2-ylidene acetonitrile or 5-chlorovaleryl chloride according to the methods described in WO 93/10100 and WO 94/08999.

The carbamation reaction of the compound of formula (II) per se can be carried out with reference to known reaction conditions (see, for example, JP-A H5-170726).

The compound of formula (I) provided by the present invention has superior herbicidal efficacy and is useful as a herbicide as is clear from the results of the herbicidal activity tests described in Test Examples 1 to 4 to be subsequently described.

The compound of formula (I) of the present invention has activity against numerous types of crop weeds and non-crop weeds. Examples of cultivated plants include gramineous plants such as rice, wheat, barley, corn, oats or sorghum, broadleaf crops such as soybeans, cotton, beets, sunflowers or rapeseed, fruit trees, vegetables such as fruit vegetables, root vegetables or leafy vegetables, and grasses, and the compound of formula (I) can be used for the cultivation thereof.

The compound of the present invention has herbicidal efficacy against the various weeds listed below that cause problems in rice paddies in any of the treatment methods of soil treatment in an irrigated or unirrigated state, soil incorporation treatment and foliar treatment. Although the following lists examples thereof, these weeds are not limited to the following examples.

Examples of paddy weeds that can be controlled by the compound of formula (I) of the present invention include Alismataceous weeds such as Alisma canaliculatum, Sagittaria trifolia or Sagittaria pygmaea, Cyperaceous weeds such as Cyperus difformis, Cyperus serotinas, Scirpus juncoides, Eleocharis kuroguwai, Scirpus planiculmis or Scirpus nipponicus, Scrophulariaceous weeds such as Lindernia procumbens, Lindernia dubia subsp. dubia or Lindernia dubia, Pontederiaceous weeds such as Monochoria vaginalis or Monochoria korsakowii, Potamogetonaceous weeds such as Potamogeton distinctus, Lythraceous weeds such as Rotala indica or Ammannia multiflora, Asteraceous weeds such as Bidens tripartita or Bidens frondosa, Leguminoseous weeds such as Aeschynomene indica, Commelinaceous weeds such as Murdannia keisak, and Gramineous weeds such as Echinochloa oryzicola, Echinochloa crus-galli var. crus-galli, Echinochloa crus-galli var. formosensis, Echinochloa crus-galli var. praticola, Echinochloa crus-galli var, caudata, Leptochloa chinensis, Leersia japonica, Paspalum distichum or Leersia oryzoides.

In addition, the compound of the present invention has herbicidal efficacy against the various weeds listed below that cause problems in field land and non-arable land in any of the treatment methods of soil treatment, soil incorporation treatment and foliar treatment. Although the following lists examples thereof, these weeds are not limited to the following examples.

Examples thereof include broadleaf weeds, including Solanaceous weeds such as Solanum nigrum or Datura stramonium, Malvaceous weeds such as Abutilon avicennae, Sida spinosa or Convolvulus arvensis, Convolvulaceous weeds such as Ipomoea pupurea, Amaranthaceous weeds such as Amaranthus lividus, Amaranthus retro flexus, Amaranthus palmeri or Amaranthus tuberculatus, Asteraceous weeds such as Xanthium strumarium, Ambrosia artemisiilifolia, Galinsoga ciliata, Cirsium arvense, Senecio vulgaris, Stenactis annuus, Galinsoga parviflora, Sonchus arvensis, Sonchus oleraceus or Matricaria indora, Brassicaceous weeds such as Rorippa indica, Sinapis arvensis, Capsella bursa-pastoris or Thlaspi arvense, Polygonaceous weeds such as Persicaria longiseta, Fallopia convolvulus, Polygonum aviculare var. condensatum, Polygonum aviculare var. monospeliense, Polygonum persicaria, Persicaria lapathifolia var. incana or Persicaria lapathifolia var. lapathifolia, Portulacaceous weeds such as Portulaca oleracea, Chenopodiaceous weeds such as Chenopodium album, Chenopodium ficifolium, Kochia scoparia or Atriplex patula, Caryophyllaceous weeds such as Stellaria media, Scrophulariaceous weeds such as Veronica persica, Commelinaceous weeds such as Commelina communis, Lamiaceous weeds such as Lamium amplexicaule, Lamium purpureum or Galeopsis tetrahit; Euphorbiaceous weeds such as Euphorbia supina or Euphorbia maculata, Rubiaceous weeds such as Galium spurium, Galium spurium var. Echinospermon, Rubia argyi or Galium aparine, Violaceous weeds such as Viola mandshurica or Viola arvensis, Boraginaceous weeds such as Myosotis arvensis, and Leguminoseous weeds such as Sesbania exaltata or Cassia obfusitolia, and Gramineous weeds such as Sorghum bicolor, Panicum dichotomiflorum, Sorghum halepense, Echinochloa crus-galli var. crus-galli, Digitaria ciliaris, Avena fatua, Eleusine indica, Setaria viridis, Alopecurus aequalis, Poa annua, Agropyron repens, Cynodon dactylon, Digitaria sanguinalis, Setaria pumila or Alopecurus myosuroides, and Cyperaceous weeds such as Cyperus rotundus.

Moreover, the compound of the present invention is also able to control a wide range of weeds growing in mowed swaths, fallow land, orchards, grasslands, lawn grass plots, train line caps, vacant land and. forest land, or on farm roads, causeways and other non-crop land.

Moreover, the compound of formula (I) of the present invention does not demonstrate phytotoxicity that becomes a problem for paddy rice in the case of any cultivation method such as direct seeding cultivation or transplantation cultivation of paddy rice.

The compound of formula (I) of the present invention can be applied before or after plant germination and can be mixed into soil before seeding.

Although the dosage of the compound of formula (I) of the present invention can be varied over a wide range corresponding to the type of compound, type of target plant, application window, location of application, properties of desired effects and the like, and as a general reference thereof, the dosage can be within the range of about 0.01 g to 100 g, and preferably about 0.1 g to 10 g, as the amount of active compound per are.

Although the compound of formula (I) of the present invention can be used alone, a formulation assistant and the like is normally incorporated in the compound of formula (I) in accordance with ordinary methods, and although there are no limitations thereon, it is preferably formulated and used in any arbitrary drug form such as a dustable powder, emulsifiable concentrate, oil miscible liquid, solubilizing agent, suspo-emulsion, fine granule, aerosol spray, less drifting dust, micro granules fine, fine grains F, granules, wettable powder, water dispersible granules, flowable concentrate, throw-in types (Jumbo), tablets, paste, emulsion in oil, water soluble powder, water soluble granules, soluble concentration or capsule suspension.

There are no limitations on formulation assistants able to be used for formulation, and examples include solid vehicles, liquid vehicles, binders, thickeners, surfactants, anti-freezing agents and preservatives.

Examples of solid vehicles include, but are not limited to, talc, bentonite, montmorillonite, clay, kaolin, calcium carbonate, sodium carbonate, sodium bicarbonate, mirabilite, zeolite, starch, acidic clay, diatomaceous earth, chaoite, vermiculite, slaked lime, vegetable powder, alumina, activated carbon, sugars, hollow glass, silica sand, ammonium sulfate and urea.

Examples of liquid vehicles include, but are rot limited to, hydrocarbons (such as kerosene or mineral oil), aromatic hydrocarbons (such as toluene, xylene, dimethyl naphthalene or phenyl xylyl ethane), chlorinated hydrocarbons (such as chloroform or carbon tetrachloride), ethers (such as dioxane or tetrahydrofuran), ketones (such as acetone, cyclohexanone or isophorone), esters (such as ethyl acetate, ethylene glycol acetate or dibutyl maleate), alcohols (such as methanol, n-hexanol or ethylene glycol), polar solvents (such as N,N-dimethylformamide, dimethylsulfoxide or N-methylpyrrolidone) and water.

Examples of binders and thickeners include, but are not limited to, dextrin, sodium salts of carboxymethyl cellulose, polycarboxylic acid-based polymer compounds, polyvinylpyrrolidone, polyvinyl alcohol, sodium lignin sulfonate, calcium lignin sulfonate, sodium polyacrylate, gum arabic, sodium alginate, mannitol, sorbitol, bentonite-based mineral matter, polyacrylic acid and derivatives thereof, chaoite and natural sugar derivatives (such as xanthan gum or guar gum).

Examples of surfactants include, but are not limited to, anionic surfactants such as fatty acid salts, benzoates, alkylsulfosuccinates, dialkylsulfosuccinates, polycarboxylates, alkyl sulfate ester salts, alkyl sulfates, alkyl aryl sulfates, alkyl diglycol ether sulfates, alcohol sulfate ester salts, alkyl sulfonates, alkyl aryl sulfonates, aryl sulfonates, lignin sulfonates, alkyl diphenyl ether disulfonates, polystyrene sulfonates, alkyl phosphate ester salts, alkyl aryl phosphates, styryl aryl phosphates, polyoxyethylene alkyl ether sulfate ester salts, polyoxyethylene alkyl aryl ether sulfates, polyoxyethylene alkyl aryl ether sulfate ester salts, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkyl aryl phosphate ester salts or salts of naphthalene sulfonate-formalin condensates, and nonionic surfactants such as sorbitan fatty acid esters, glycerin fatty acid esters, fatty acid polyglycerides, fatty acid alcohol polyglycol ethers, acetylene glycol, acetylene alcohol, oxyalkylene block polymers, polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers, polyoxyethylene styryl aryl ethers, polyoxyethylene glycol alkyl ethers, polyoxyethylene fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyoxyethylene hydrogenated castor oil or polyoxypropylene fatty acid esters.

Examples of anti-freezing agents include, but are not limited to, ethylene glycol, diethylene glycol, propylene glycol and glycerin.

Examples of preservatives include, but are not limited to, benzoic acid, sodium benzoate, methyl paraoxybenzoate, butyl paraoxybenzoate, isopropyl methyl phenol, benzalkonium chloride, chlorhexidine hydrochloride, aqueous hydrogen peroxide, chlorhexidine gluconate, salicylic acid, sodium salicylate, zinc pyrithione, sorbic acid, potassium sorbate, dehydroacetic acid, sodium dehydroacetate, phenoxyethanol, isothiazoline derivatives such as 5-chloro-2-methyl-4-isothiazolin-3-one or 2-methyl-4-isothiazolin-3-one, 2-bromo-2-nitropropane-1,3-diol and salicylic acid derivatives.

The previously mentioned solid vehicles, liquid vehicles, binders, thickeners, surfactants, anti-freezing agents and preservatives can each be used alone or in a suitable combination thereof corresponding to the purpose of use and the like.

Although the incorporated ratio of the compound of formula (I) of the present invention with respect to the total herbicide composition. of the present invention can be increased or decreased as necessary and there are no particular limitations thereon, it is normally about 0.01% by weight to 90% by weight, and for example, in the case of being in the form of a dustable powder or granules, is preferably about 0.1% by weight to 50% by weight and more preferably about 0.5% by weight to 10% by weight, while in the case of being in the form of an emulsifiable concentrate, wettable powder or water dispersible granules, is preferably about 0.1% by weight to 90% by weight and more preferably about 0.5% by weight to 50% by weight.

These preparations can be provided for use in various types of applications by diluting to a suitable concentration as necessary followed by spraying or applying directly to plant foliage, soil or the surface of a rice paddy and the like.

The following provides an explanation of the present invention through examples thereof.

EXAMPLES Example 1 Method for the Synthesis of Methyl N-(3-chloro-4,5,6,7-tetrahydropyrazolo[1,5-a]pyridine-2-yl)-4-cyanopyr azol-5-yl)-N-ethoxycarbonyl Carbamate (Compound 1)

5-amino-1-(3-chloro-4,5,6,7-tetrahydropyrazolo[1,5-a]pyridin-2-y l)pyrazole-4-carbonitrile (1 g) was dissolved in N,N-dimethylformamide (5 ml) followed by the addition of methyl chloroformate (1.6 g) thereto. Sodium hydride (0.4 g) was added while cooling with ice followed by heating to reflux for 2 hours. Following completion of the reaction, water was added to the reaction solution followed by extraction with ethyl acetate. After drying with sodium sulfate, a crude product obtained by distilling off the solvent under reduced pressure was washed with isopropyl ether to obtain the desired compound (1.3 g).

The starting material in the form of the compound of formula (II) was synthesized in accordance with WO 93/10100 and WO 94/08999.

The examples listed in the following tables can be synthesized by the same manner as the above-mentioned methods or obtained in the same manner as the above-mentioned methods.

TABLE 1

Com- Refractive pound R¹ R² R³ R⁴ a X mp index (° C.) 1 Cl CN Me Me 4 O 136-137 2 Cl CN Me Me 3 O 108-110 3 Cl NO₂ Me Me 4 O 155-156 4 Br CN Me Me 4 O 154-155 5 Br NO₂ Me Me 4 O 148-149 6 Cl CN Et Et 4 O 79-80 7 Cl NO₂ Et Et 4 O 1.5454 (24.7) 8 Br CN Et Et 4 O 120-121 9 Br NO₂ Et Et 4 O 105-106 10 Cl NO₂ n- n- 4 O 84-85 propyl propyl

TABLE 2 Refractive Compound R¹ R² R³ R⁴ a X mp index (° C.) 11 Br NO₂ n-propyl n-propyl 4 O 86-87 12 Cl CN isopropyl isopropyl 4 O 112-113 13 Cl CN isobutyl isobutyl 4 O 1.5248(23.2) 14 Cl CN allyl allyl 4 O 1.5502(23.2) 15 Cl NO₂ allyl allyl 4 O 84-85 16 Br CN allyl allyl 4 O 80-81 17 Br NO₂ allyl allyl 4 O 98-99 18 Cl CN 2-chloroethyl 2-chloroethyl 4 O 128-130 19 Cl CN 2,2,2-trichloroethyl 2,2,2-trichloroethyl 4 O 20 Cl CN Et Et 4 S 1.5817(22.3) 21 Cl NO₂ Et Et 4 S 1.5834(28.1) 22 Br CN Et Et 4 S 1.5762(26.2) 23 Br NO₂ Et Et 4 S 1.5890(28.3) Preparation Examples

1. Dustable Powder

Compound of formula (I) 10 parts by weight Talc 90 parts by weight

A dustable powder is obtained by mixing the above components and finely crushing with a hammer mill.

2. Wettable Powder

Compound of formula (I)   10 parts by weight Polyoxyethylene alkyl aryl ether sulfate 22.5 parts by weight White carbon 67.5 parts by weight

A wettable powder is obtained by mixing the above components and finely crushing the mixture with a hammer mill.

3. Flowable Concentrate

Compound of formula (I) 10 parts by weight Polyoxyethylene alkyl ether phosphate 10 parts by weight Bentonite  5 parts by weight Ethylene glycol  5 parts by weight Water 70 parts by weight

A flowable concentrate is obtained by mixing the above components and crushing using a wet pulverizer.

4. Emulsifiable Concentrate

Compound of formula (I) 15 parts by weight Ethoxylated nonylphenol 10 parts by weight Cyclohexanone 75 parts by weight

An emulsifiable concentrate is obtained by mixing the above components.

5. Granules

Compound of formula (I)  5 parts by weight Calcium lignin sulfonate  3 parts by weight Polycarboxylate  3 parts by weight Calcium carbonate 89 parts by weight

The above components are mixed followed by adding water, kneading, extruding and granulating. Subsequently, granules are obtained by drying followed by sizing.

<Biological Testing Examples>

1. Paddy Herbicidal Activity Test

Rice paddy soil was filled into a 1/10000 are pot followed by the addition of suitable amounts of water and chemical fertilizer, kneading, seeding with Echinochloa crus-galli, Monochoria vaginalis and Scirpus juncoides and maintaining in an irrigated state at a water depth of 3 cm.

Wettable powders of Target Compound (I) shown in Table 1 prepared in compliance with the preparation examples were diluted with a suitable amount of water, rice plants in the 2.0 leaf stage were transplanted during 3.5 leaf stage of Echinochloa crus-galli, and treated by dropping in chemical in the prescribed amount per 10 are using a pipette.

After treating for 30 days in a glass greenhouse at an average atmospheric temperature of 30° C., the herbicidal efficacy thereof was investigated.

Evaluation of herbicidal efficacy was carried out by comparing growth inhibition rate (%) with an untreated group, while evaluation of phytotoxicity was carried out by comparing growth inhibition rate (%) with the state of a complete eradication group, and were evaluated at 11 levels indicated below.

0 (exponent): 0% to less than 10% (growth inhibition rate)

1: 10% to less than 20%

2: 20% to less than 30%

3: 30% to less than 40%

4: 40% to less than 50%

5: 50% to less than 60%

6: 60% to less than 70%

7: 70% to less than 80%

8: 80% to less than 90%

9: 90% to less than 100%

10: 100%

The results are shown in Table 2.

Control agent 2.28 (described in WO 94/08999)

TABLE 2 5g^(a.i.)/10a 1g^(a.i.)/10a Echinochloa Scirpus Monochoria Oryza Echinochloa Scirpus Monochoria Oryza Compound crus-galli juncoides vaginalis sativa crus-galli juncoides vaginalis sativa 1 10 9 10 0 9 9 10 0 4 10 10 10 1 10 9 10 0 5 9 10 10 1 9 10 10 1 6 10 10 10 1 10 9 10 0 8 10 9 10 1 10 9 10 0 14 10 10 10 1 10 9 10 1 2.28 2 2 4 1 1 1 3 0

2. Farming Soil Treatment Test

Field soil was filled into a 1/6000 are pot followed by seeding with Digitaria cilaris, Chenopodium album and Amaranthus retroflexus and covering with soil.

Wettable powders of compounds of formula (I) shown in Table 1 prepared in compliance with the preparation examples were diluted. with water to the prescribed amount of chemical and uniformly sprayed onto each soil surface layer using 100 liters of sprayed water per 10 are prior to weed growth following seeding.

After treating for 30 days in a glass greenhouse at an average atmospheric temperature of 30° C., the herbicidal efficacy thereof was investigated.

Evaluation of herbicidal efficacy was carried out in the same manner as the above-mentioned Test Example 1.

The results are shown in Table 3.

TABLE 3 10g^(a.i.)/10a 5g^(a.i.)/10a Digitaria Chenopodium Amaranthus Digitaria Chenopodium Amaranthus Compound ciliaris album retroflexus ciliaris album retroflexus 1 9 10 9 9 9 9 4 10 10 10 10 9 10 5 9 10 10 9 10 10 6 10 10 10 10 9 10 8 10 9 10 10 9 10 14 10 10 10 10 9 10 2.28 2 5 5 1 4 3

3. Weed Foliar Treatment Test

Soil was filled into a 1/6000 are pot followed by seeding with Digitaria ciliaris, Chenopodium album and Amaranthus retroflexus, covering with soil, and cultivating in a glass greenhouse at an average atmospheric temperature of 25° C.

Wettable powders of Target Compound (I) shown in Table 1 prepared in compliance with the preparation examples were diluted with water to the prescribed amount of chemical and uniformly sprayed onto the weeds using 150 liters of sprayed water per 10 are when Digitaria ciliaris had grown to the 1.0 to 2.0 leaf stage.

After treating for 3 weeks in a glass greenhouse at an average atmospheric temperature of 25° C., the herbicidal efficacy thereof was investigated.

Evaluation of herbicidal efficacy was carried out in the same manner as the above-mentioned Test Example 1.

The results are shown in Table 4.

TABLE 4 10g^(a.i.)/10a 5g^(a.i.)/10a Digitaria Chenopodium Amaranthus Digitaria Chenopodium Amaranthus Compound ciliaris album retroflexus ciliaris album retroflexus 1 10 10 10 9 10 10 4 10 10 10 10 10 10 5 10 10 10 9 10 10 6 10 10 10 10 10 10 8 10 10 10 10 10 10 14 10 10 10 10 10 10 2.28 4 7 6 2 6 3

4. Weed Foliar Treatment Test

Field soil was filled into a 1/4500 are pot followed by seeding with Digitaria ciliaris and Galinsoga parviflora, covering with soil and cultivating in a glass greenhouse at an average atmospheric temperature of 25° C.

Wettable powders of Target Compound (I) shown in Table 1 prepared in compliance with the preparation examples were diluted with water to the prescribed amount of chemical and uniformly sprayed onto the weeds using 100 liters of sprayed water per 10 are when Digitaria ciliaris had grown to the 4.0 to 5.0 leaf stage (plant height: 10 cm to 15 cm).

After treating for 20 days in a glass greenhouse at an average atmospheric temperature of 25° C., the herbicidal efficacy thereof was investigated.

Evaluation of herbicidal efficacy was carried out in the same manner as the above-mentioned Test Example 1.

The results are shown in Table 5.

TABLE 5 10 g^(a.i.)/10a Compound Digitaria ciliaris Galinsoga parviflora 1 9 10 3 10 10 4 10 10 5 9 10 6 10 10 8 10 10 12 10 10 13 10 10 14 10 10 15 10 10 2.28 1 2

INDUSTRIAL APPLICABILITY

According to the present invention, the compound for formula (I) of the present invention is useful as a herbicide against harmful plants since it has superior herbicidal efficacy against undesirable plants. 

The invention claimed is:
 1. A compound represented by the following formula (I):

wherein, R¹ represents a chlorine atom or bromine atom, R² represents a cyano group or nitro group, R³ and R⁴ may be the same or different and represent C₁-C₆ alkyl groups which may be optionally substituted with one or more halogen atoms, C₃-C₆ alkenyl groups which may be optionally substituted with one or more halogen atoms, or C₃-C₆ alkynyl groups which may be optionally substituted with one or more halogen atoms, a represents 3 to 5, and X represents an oxygen atom or sulfur atom.
 2. The compound according to claim 1, wherein R³ and R⁴ may be the same or different and represent C₁-C₄ alkyl groups which may be optionally substituted with one or more halogen atoms, or C₃-₅ alkenyl groups which may be optionally substituted with one or more halogen atoms, and a represents
 4. 3. A herbicide composition containing a herbicidally effective amount of at least one compound according to claim
 1. 4. The herbicide composition according to claim 3, further containing a formulation assistant.
 5. A method for controlling undesirable plants, said method comprising the step of applying an effective amount of at least one compound according to claim 1 to an undesirable plant or the location of the undesirable plant.
 6. A herbicide composition containing a herbicidally effective amount of at least one compound according to claim
 2. 7. The herbicide composition according to claim 6, further containing a formulation assistant.
 8. A method for controlling undesirable plants, said method comprising the step of applying an effective amount of at least one compound according to claim 2 to an undesirable plant or the location of the undesirable plant.
 9. A method for controlling undesirable plants, said method comprising the step of applying an effective amount of the herbicide composition according to claim 3 to an undesirable plant or the location of the undesirable plant.
 10. A method for controlling undesirable plants, said method comprising the step of applying an effective amount of the herbicide composition according to claim 6 to an undesirable plant or the location of the undesirable plant.
 11. A method for controlling undesirable plants, said method comprising the step of applying an effective amount of the herbicide composition according to claim 4 to an undesirable plant or the location of the undesirable plant.
 12. A method for controlling undesirable plants, said method comprising the step of applying an effective amount of the herbicide composition according to claim 7 to an undesirable plant or the location of the undesirable plant. 